i'm gwen ifill of "the newshour" and "washington week" on pbs, and i welcome you to the first and the only vice presidential debate between vice president dick cheney, the republican nominee, and senator john edwards, the democratic nominee. these debates are sponsored by the commission on presidential debates. tonight's will last 90 minutes, following detailed rules of engagement worked out by representatives of the candidates. i have agreed to enforce the rules they have devised for themselves to the best of my ability. the questions tonight will be divided between foreign and domestic policy, but the specific topics were chosen by me. the candidates have not been told what they are. the rules -- for each question, there can be only a two- minute response, a 90-second rebuttal and, at my discretion, a discussion extension of one minute. a green light will come on when 30 seconds remain in any given answer, yellow at 15 seconds, red at five seconds, and then flashing red means time's up. there's also a back-up buzzer system, if needed. candidates may not direct questions to one anoth